1. Field of the Invention
This invention described herein relates in general to medical stress test measuring apparatuses, methods, and specialized exercise equipment. In particular, it relates to an improved apparatus for cardiac stress testing, methods for cardiac stress testing, and specialized exercise equipment.
2. Description of Related Art
Some heart abnormalities do not show up in an electrocardiogram taken when the patient is at rest. However, it may be possible to induce the heart to beat faster, which may reveal abnormalities not otherwise diagnoseable. In order to stress the heart, there are two widely used protocols. One is called the Bruce protocol. In the Bruce protocol, the individual to be tested is placed on a treadmill inclined at a grade of 10 percent. The treadmill begins to move and an individual begins to walk on the treadmill in order to remain in the same place. The person's heart condition is monitored by an electrocardiogram. During the Bruce protocol the blood pressure is periodically checked. The speed and inclined grade of the treadmill is increased in stages causing an individual being tested to have to walk faster and work harder because of the steeper incline to stay in the same place. In this fashion, it is hoped an appropriate elevated heart rate will be achieved. Ideally, an individual should reach 90% of their maximum predicted heart rate for their age before having to terminate the test. This test presents challenges for some individuals. Some people have orthopedic problems like a bad knee that make it difficult or impossible to perform the walking required. Other conditions which can make it difficult for an individual to perform the exercise in the Bruce protocol include various forms of arthritis, diabetic problems like ulcers or neuropathy, and peripheral vascular disease. Moreover, the abrupt increase in the exercise loads required in the Bruce protocol are difficult or impossible for patients who have impaired respiratory function including those with COPD and asthma. Ordinarily, patients who cannot perform the exercise required in a Bruce protocol, follow a protocol called the Persantine cardiolyte stress test. There a person is placed on a table with an intravenous inlet port. A drug (dipyridaxide), called by the trade name, Persantine, is infused through the IV port. Persantine causes the heart to beat at an increased rate. Persantine dilates the coronary arteries and accelerates the heart rate. Photographic images are taken with an x-ray machine using cardiolyte or thallium. This helps the cardiologist determine if the patient has ischemia by analyzing the images taken during times of physical stress and at rest. The ischemic portion of the heart will appear differently because it will not illuminate through the cardiolyte or thallium as well as a fully profused part of the heart. Many people have unpleasant reactions to Persantine, which include headache, dizziness, flushed skin, and, shortness of breath. For many people, the effect of having the heart beat very hard is both unpleasant and anxiety provoking.
A variety of devices have been proposed to improve or modify the application of stress and exercise both in cardiac testing and in other circumstances. For example, Yurdin U.S. Pat. No. 4,372,531 proposes a cardiac stress table to be used in a cardiac nuclear imaging procedure. This procedure usually requires a patient to be motionless on a table while being scanned. Yurdin combines a tiltable table for supporting a patient in a restrained position combined with a stationery bicycle-like device to enable one to combine an exercise stress challenge with a nuclear imaging test. Jordan U.S. Pat. No. 5,746,684 proposes an exercise stand that includes a stationery bicycle-like pedal arrangement along with a variety of hand holds. Jordan proposes that the hand holds can isometrically exercise the upper body while the pedal device isotonically exercises the lower extremities. Gezari U.S. Pat. No. 4,285,515, proposes an improved table, which includes a stationery bicycle-like device, as well as tilting moveable support for a patient. This provides for support during exercise for scintillation camera scanning. Platzker U.S. Pat. No. 5,313,942 proposes an improved electrode system for administering an EKG test, which also provides a chair with removable exercise accessories. The electrodes are embedded in a strap which passes around a patient's chair. A stationery bicycle or hydraulic pusher device may be provided to a patient to provide exercise stress during an EKG test.
For many individuals, especially individuals with impaired cardiac or respiratory systems, standard exercise equipment proves unsatisfactory for achieving satisfactory heart rates. For such an individual, consider a resistance based stationary bicycle exercise equipment. With this kind of exercise equipment one may adjust the amount of resistance or effort that is required for an individual to turn the pedals. At a certain preset level of resistance, the faster one pedals, the greater work one does, hence the greater amount of energy is expended, which tends to elevate the heart rate and to increase the breathing rate to increase the body's metabolism to meet the demands imposed by the work load required by a bicycle. In this kind of arrangement, a problem arises for certain individuals. If the resistance level is set low, the individual can comfortably work the device but will have difficulty achieving sufficient speed to induce the required work load, hence elevate the heart rate to a desired level. If the resistance is set relatively high, then the individual may stop because of leg muscle fatigue or cramping before the appropriate heart rate is achieved. There are stationary exercise bicycles which function in a different fashion. One is sold under the trade name of Kettler. This uses an electromagnetic force on a flywheel to induce resistance to motion of the pedals. The electromagnetic force can be easily varied by a controller to increase or decrease the force required to move the pedals, hence the work load required to operate the Kettler exercise bicycle. However, typically, the Kettler exercise bicycle is used by highly conditioned individuals trying to improve their exercise efficiency. That is, they will set the bicycle so that they will perform at a certain constant RPM. This is the level at which they are able to efficiently use their legs to pedal the bicycle, while maintaining proper form. The Kettler bicycle will then impose a gradually increasing work load on the individual enabling them to train to maintain their most efficient pedaling stroke at a higher work load. Neither of the above type of machines function adequately for an unconditioned individual who may have impairments like arthritis or a limited ability to pedal a stationary bicycle or to maintain a particular speed under increasing work loads.